a) Field of the Invention
The invention is directed to a process and arrangement for monitoring and controlling the treatment parameters in an ophthalmic treatment device, especially for adjusting and monitoring the application of the actual amount of radiation (treatment parameter) to be applied to the specific patient in photodynamic therapy (PDT) of diseased tissue in the fundus of the eye, especially for the treatment of age-related macular degeneration which usually leads to a (progressive) destruction of the central retinal portions with irreversible loss of visual function. In the proliferative form of macular degeneration, a neovascularization which originates in the choroid and destructively grows under and into the retina of the eye is responsible for the course of the disease. Harmful scarring occurs in the end stage.
b) Description of the Related Art
It is known to isolate thromboses and neovascularization in the eye through photodynamic therapy in that a selective and localized treatment of the affected locations and tissue parts of the eye is carried out through photodynamic effects. For targeted implementation of such treatment of diseased tissue, the patient is injected with photosensitizers which selectively concentrate in diseased tissue parts of the eye after a certain period of time and enable effective radiation treatment with laser light of suitable wavelength.
Lasers are preferably used for photosensitization after injection with sensitizers, these lasers emitting a wavelength of adjustable output suitable for exciting the photosensitization, wherein the adjusted output value depends, among other things, on the injected dye and on any opacity which may be present in the eye to be treated.
The light emitted by the laser is coupled into an applicator via suitable optical elements, e.g., light guides, wherein the light is directed onto the portion of the retina of the eye to be treated by means of the applicator. The setting parameters, such as the diameter of the treatment area and the radiation output, are determined and adjusted by the treating physician.
A target beam which assists the physician in orienting the applicator in such a way that a treatment beam can expose the surface to be treated in the eye is generated by a second, substantially weaker laser which emits light of a different wavelength. This target beam is also coupled into the applicator through the optical elements.
Treatments should take into account patient-related parameters such as the size of the area to be treated in the eye, consideration of the influence of any opacity that may be present in the eye of the patient, and maintaining a defined maximum radiation intensity and dye-related parameters (energy flux density). However, in currently used laser systems, only the parameters of output, energy and duration of irradiation can be adjusted in the device. Thus, it is disadvantageous that in order to adapt the actual parameters to be used the physician or user must convert the individual values by means of tables or other means and must guarantee that these values are maintained. This method is a source of human error on the part of the physician or user and can have direct consequences on the success of the treatment.